Auschwitz was originally constructed as a labor camp for Polish prisoners in 1940, but was used to incarcerate — and kill — everyone from Jews to Gypsies to Soviet prisoners of war to homosexuals and conscientious objectors.

— The entrance to the main camp, Auschwitz, contains the notorious sign "Arbeit macht frei," German for "work will set you free."

— Birkenau was built in October 1941 and was the site of the gas chambers and crematoria. By 1944, some 6,000 people a day were executed there.

— As many as 1.5 million people, mostly Jews, were killed at the camps, as well as homosexuals, Gypsies, political prisoners, conscientious objectors, Soviet POWs and those with disabilities.

— The camp was liberated by Soviet forces on Jan. 27, 1945.